Rotatable electrical potentiometer connection



Oct. 2l, 1952 w. .1. o eocENsKY ROTATABLE ELECTRICAL POTENTIOMETER CONNECTION Filed Aug. 25, 194e 2 SHEETS-SHEET l R W @www Nw .R WC O VNG n O J. mm A L L Patented Oct. 21, 1952 ROTATABLE ELECTRICAL POTENTIOMETER CONNECTION Willard J. Opocensky, Glendale, Calif., assigner to Librascope, Incorporated, Glendale, Calif., a corporation of California,

Application August 25, 1948, Serial No. 46,029

7 Claims. l

This invention relates to new and useful improvements in rotatable electrical potentiometer connection, and is more particularly directed to means to compensate for the unavoidable shocks and jars or vibrations transmitted from all directions to potentiometers under certain operating conditions and uses, as well as those set updirectly by certain frequencies of vibrations or the harmonics thereof causing a sympathetic vibration of the commercial form of contact arms bearing against the slip rings of the potentiometers.

The shocks, jars or vibrations from whatever cause, if of sufficient intensity, will operate to effect a rapid opening and closing of the potentiometer circuits to cause the faulty operation thereof and such operation may be accompanied by arcing between the slip rings and contact arms resulting in the formation of pits in the contact faces of the slip rings and brushes, with loss of eiciency and damage to the parts.

Heretofore, attempts have been made to overcome the possibility of a disconnection of the contact arms from the slip rings by providing stronger springs to hold the contact arms engaged with their slip rings, but this not only failed to prevent disconnection of the contact arms and slip rings under the influence of a shock or jar of an intensity or force greater than the tensions of the springs, but introduced an additional disadvantage in that the excessive spring pressure of the contacts against the surfaces of their cooperating slip rings thus required created frictional losses that increased considerably the power requirements for the mechanisms that might be designed to operate the potentiometer shafts.

- This difficulty is emphasized when a plurality of such potentiometers are disposed co-axially for the rotation of the respective contact arms by a common shaft which serves, of course, to multiply the torque required to overcome the friction created by the strong springs of the contact arms that cooperate with the slip rings.

With the spring pressure lightened to a point where the potentiometer shaft might be rotated in a positive and accurate manner requiring a minimum of power, the contact arms Would vibrate sympathetically at certain frequencies of vibration set up by various operating conditions to cause a rapid opening and closing of the circuits of the potentiometer whether or not arranged co-axially on a common shaft. The potentiometers may be employed in circuits that may be utilized to effect the rapid rotation and other movements of devices under the control of various types of instruments and such opening and closing of the circuits due to the vibratory action of the contact arms from any source would operate the devices erratically to the detriment of the purposes of the devices.

One object of the present invention is to provide novel and very simple means for maintaining engagement between the stationary and movable elements of a potentiometer or other types of electrical mechanisms employing slip rings and contact arms or the like, with no increase in the tensions of the means normally employed to maintain frictional contact between such stationary and movable elements and for the positive maintenance of such contact despite vibran tions from mechanical shocks or jars and including those of great force and intensities or from electrical or other sources.

Another object of the invention is to provide at least two brush or contact arms, one of which is off-set from the other so that brushes thereof contact different portions of the slip ring. Thus, by relatively off-setting the respective brush or contact arms, the brushes on the free ends of the arms contact different concentric zones of the slip ring and thereby reduce the wear by at least one-half, the contact surfaces on said arms and said slip ring defining a common plane of engagement.

By designing the brush or contact arms of respectively different shapes or sizes the vibrai tions of various ranges and the harmonics set up mechanically or otherwise and which might affect either of said arms alone, to cause its rapid engagement with and disengagement from the slip ring, will have no effect on its companion arm, as only one such range of vibrations occurs at a time and that arm which is unaffected sympathetically will maintain the potentiometer circuit closed under all practical operating conditions.

This application represents Va continuation in part of my parent application led March 11, 1946, Serial No. 653,549 entitled Potentiometer, now Patent No. 2,461,843 issued February 15, 1949.

Further and more specifically stated objects, features and advantages will more clearly appear from a consideration of the following detailed description, especially in connection with the accompanying drawings which form part of the specification and which illustrate the invention.

Whereas the drawings show a single potentiometer which is sufcient to disclose the invention, the discovery is adapted for use in connection with a series of co-axial potentiometers mounted along a common operating shaft, the movement of which shaft effects the adjustment of resistance contact arms individual to the respective potentiometers, while permitting the respective contact arms to be independently set to relatively different positions.

In the accompanying drawings, Fig. 1 is a plan view of a potentiometer equipped with my invention, partly in cross-section, taken on line I-I of Fig. 2;

Fig. 2 is a view in front elevation, showing the offset contacts of the contact arms with the slip ring;

Fig. 3 is a vertical cross-sectional view taken on the line 3-3 of Fig. 1, and showing one edge of the contact arm unit, with its support;

Figs. 4 and 5 are top plan and cross-sectional vertical views, respectively, of the wiper contact arm of the potentiometer, which sweeps over the potentiometer coils; and

Fig. 6 is a detail perspective view taken from beneath, showing one form of the brush-supporting or contact arms of this invention, wherein engagement between the brushes and the contact ring occurs in a flat plane.

The invention is capable of co-action with the slip rings of other forms of potentiometers as Well as other types of electrical devices employing slip rings and contact arms, but to emphasize its relation to the parent application, Serial No. 653,549 iiled March 11, 1946, now Patent No. 2,461,843 issued February 15, 1949 as above noted, the invention will be explained in connection with the potentiometer of the original application.

Such potentiometer comprises a base plate I0, and if the potentiometers are to be used in multiple, a base plate is provided for each unit potentiometer, as indicated in Fig. 2, in which case, the base plates are spaced apart by supporting sleeves or separators I I, the entire assemblage being secured together by rods I2 extending through the bases and sleeves, to enable a series of potentiometers to be operated in a gang, if desired.

An operating shaft I3 extends through the base plate or series of base plates I0, as the case may be. A ring-like bushing 24 is tightly tted in an annular opening formed centrally through each base plate, and bearings 40 through which the shaft passes, co-act with the bushings to insure that the operating shaft shall be held centrally of the bushings 24. The operating shaft I3 is provided with an insulated collar or slip ring I4 for each potentiometer on the shaft, each collar or slip ring having secured thereto or integral therewith a wiper contact arm I extending at substantially right angles to the operating shaft and of a length to enable the bearing face of the Wiper arm to ride or sweep over the exposed coils 3| of a potentiometer coil unit encircling the shaft, upon turning the shaft.

As shown in Figs. 4 and 5, the slip ring I4 is provided with a metallic bushing 42 arranged centrally of the ring and through which bushing the operating shaft I3 extends. One end 43 of the bushing 42 projects beyond the slip rings, and is provided with radially extending slits 44. A slotted or split gripping clamp 45 fits around the slitted extension 43 of the bushing, and by tightening the screw 46 of the clamp, the

bushing 42 with its slip ring I4 is secured to the operating shaft I3.

Insulation 41 interposed between and secured to, and connecting the metallic slip ring or collar I4 and the bushing 42, insulates the wiper brush supporting arm I5 from the operating shaft.

A strengthening and supporting rod 48 projects radially from the collar or slip ring I4, in line with the brush-supporting wiper arm I5. The wiper arm is bent downwardly, as at 49, and then projects outwardly to form the wiping extension 50, the lower face of which carries the wiper 5I (Fig. 5) to contact the exposed turns or coils of the resistance Wire 3l of the potentiometer. The outer end of the strengthening and supporting rod 48 passes through a hole 52 formed in the downward bend 49 of the Wiper arm I5.

The under surface of the collar or slip ring I4 is contacted by a pair of brushes I6 and I6 on opposite sides of the shaft I3. These brushes are carried by arms 53 and 54, respectively, which arms, at their outer ends, are integral with a plate 55 fixed to a block of insulating material I'I (Fig. 3) suitably supported on the block I8' mounted on the supporting block I8. By means of suitable terminals (not shown) these brushes I6, I6', may be connected to desired circuits that may also include the coil terminal connections 42 in any proper manner. Attention is called to the different shapes and positions of the arms 53 and 54. If the potentiometer is subjected to vibration, these arms will have different vibration frequencies, thereby tending to eliminate any inaccuracy in case the vibration should be so severe as to move one of the brushes momentarily out of contact with the collar I4. Also it is to be noted that the brush I6' is spaced a greater distance from the center of the shaft I3 than is the brush I6 so that the two brushes engage different contact surfaces on the slip ring which condition reduces wear.

A potentiometer coil unit is associated with each plate l0 and brush set as above described. This unit in the preferred form shown, comprises a coil-supporting block I 8 of cast metal and having a circular annular wall I9 connected by radial ribs 20 to a central hub sleeve through which the shaft I3 is adapted to extend when the coil is in position.

The coils of resistance wire 3I are wrapped around a band 30 of insulating material, encircling the outer periphery of the coil-supporting block IB, the wire lying in toroidal coils of rectangular cross-section suitably insulated from each other. The upper edges of the coils of wire 3| are exposed to be engaged by the wiper arm I5, the wiper 5I of which rests on and sweeps the upper ends of the coils. The arm I5 is made of exible conducting material which tends to hold the wiper in contact with the wire 3 I. However, if the arm I5 is moved so that the wiper 5I is out of contact with the resistance wire, that is, when it is passing across the corresponding radial slots in the block I8 and band 30, the arm l5 can move downwardly only a very slight distance before it is arrested by engaging the rigid supporting rod 48. By slightly rounding the ends of the band or core 30 of insulating material at the points 51, Fig. 2, on each side of the slot, the Wiper 5I carried by the arm I5 will not catch on these corners, but will slide onto the band 30 and the Wire 3I wound thereon. The terminals 42 are provided for the coils.

More specifically referring to the contact fingers 53, 54 and the structure disclosed in Figs. 3 and 6, it will be understood that, in addition to maintaining a closed circuit between stationary and movable elem-ents of 'a potentiometer under normal conditions, it is also an object of the present invention to continue the maintenance of a closed cir-cuit between the rfixed and movable elements when, under abnormal conditions. the potentiometers are subjected to unusu-ally heavy shocks or jars, also when due to the sympathetic vibrations set up by the contact arms in the presence of certain frequencies mechanically or otherwise encountered the potentiometer circuit tends to rapidly open and close.

To these ends, as well as to emplify the construction, the stationary contact elements are of lany suitable flexible resilient material and comprise a plate 55 secured by fastenings 55a to the upper inclined face of a block II of insulation. vThe block is supported upon a bed plate I 8 yresting on the bottom of a' reces-s formed in the upper face of the coil-supporting block I8. Fig. 3.

By locating the insulating block I1, bed plate i8 and base plate 55 in the recess in the-upper face of the coil-supporting block I8, these parts are protected from accidental injury and are out of the way of moving parts, this arrangement also conserving space. n

A pair of spaced conta-ct arms or fingers 53, 54 in lsubstantial parallelism, project from the inner edge of the base plate 55, the arms being spaced apart to extend on opposite sides of the operating shaft I3, beneath the sl'p ring I4, and

the inclined upper face of the insulating block Il is such as to bias the free ends of the arms 53, 5,4 against the under face of the slip or collector ring. Brushes I6, I on the free ends of the respective arms contact with and press against the lower face of the slip ring I4, not only because of the bias imparted to the contact arm unit by the inclined face of the insulating block I1, but also because of the inherent resilience of the arms, which are tensioned by the adjustment of the slip ring I4 axially of its bushing 42.

This arrangement issuflici-ent to maintain the contact fingers 53, 54 against the slip ring -despite the shocks and jars normally sustained by a potentiometer or other type of electrical device utilizing slip or collector rings and contact arms to maintain a closed circuit, but to prevent disengagement of the stationary contact arms from their slip ring, under unusually severe vibrations, shocks and jars, additional safe-guards are provided.

Thus, the spaced relation of the contact fingers or arms 53, 54 is such as to position the brushes I6, I6' so that one of said arms, as 53, for instance, presses its contact brush I6 against the under face -of the slip ring I4 at a point closer to the axis of rotation of the slip ring than is the point at which the brush l5' of the companion arm 54 engages the un-der face of the slip ring. As a result, the two brushes Contact respectively different concentric zones of the slip ring, as best shown in Fig. 6. The slip ring I4 and the brushes I6 and I6' are, as will be seen from the figure, arranged for planar contact.

The arrangement by which `brushes I6, I6 of the contact arms 53, 54 engage different concentric zones of the slip ring I4, not only assists in reducing wear, but also serves to maintain the circuit closed in instances where one contact becomes fouled or is otherwise ineffective.

Furthermore, the contact arm 53 is of a dif- 6, ferent shape from its companion arm 54, being considerably broader and hence has a different resonant frequency of vibration, though any other suitable difference in shape w-ould also be effective.

It will be noted that the effective lengths of the -contact arms differ, the contact arm 54 being considerably longer as well as more slender and flexible than the companion arm 53, the effective length of the latter being measured from the angle point l53h (Fig. 6) to the block I1.

The employment of multiple contact arms of different shapes will eliminate the opening of the circuit caused by vibrations of the -contact arms due to the effect of certain frequencies of vibration to which the potentiometer, for instance, may be subjected. A vibration of such frequency asy will cause the more flexible contact arm '54 to vibrate in sympathy or harmony therewith, will have no effect lon the remaining less iiexible arm 53, or vice versa and as long as one of the multiple arms remains in contact with its slip ring the circuit will not be interrupted.

The operating shaft I3 lmay be actuated manually or by instrument mechanisms and other known means associated with the shaft, not shown, for enabling they shaft with its wiper arm or arms I5 to be rotated to any desired position.

It will be understood that many changes and alterations in the mechanisms herein disclosed may be made without departing from the spirit and scope of the invention.

What is `claimed as new, is

l.. In an electrical device, the combination with a rotatable contact member having a slip ring; of a stationary contact member to co-act therewith, said stationary contact member having a plurality of nexible contact arms of substantially different effective lengths extending into engagement with the slip ring in a plane normal to the axis of rotation of said slip ring; and means having an inclined face to support the stationary contact member at an angle to the plane of the rotatable contact member to bias the stationary resilient-contact arms against the rotatable contact member.

2. In an electrical device, 'the combination with an operating sha-ft and a rotatable contact member mounted on the shaft of a stationary coilsupporting block encircling the operating shaft land having a recess formed in one end thereof; a bed plate and an insulating block thereon, both accommodated in the recess; a contact member mounted on the insulating block and having a plurality of contact arms, each having a substantially different resonant frequency, projecting into engagement with the rotatable contact member; and engaging surfaces formed on each of said contact arms and arranged each to engage said rotatable contact member in a different path.

3. In an electrical device, the combination with a stationary block around which a coil is formed, and a rotatable operating shaft encircled by the coil-supporting block; of a slip ring; means to adjustably secure the slip ring to the rotatable shaft; and a stationary contact member having a plurality of resilient contact arms, each having a substantially different vibration period projecting into engagement with the slip ring, a contact portion formed on ea-ch of said arms and arranged to engage said slip ring in an annular path differing substantially from that engaged by another of said contact portions.

4. In an electrical device, the combination with a stationary coil and a rotatable operating shaft encircled by the coil of a. slip ring, means to adjustably secure the slip ring to the rotatable shaft; and a stationary contact member having resilient contact arms projecting into engagement with the slip ring, said contact arms being of respectively different effective lengths and arranged to engage said slip ring in substantially different paths.

5. .en electrical contact device comprising, a slip ring, .a contact member including a. base member, a pair of resilient brush arms support-- ed on said base member and arranged yto engage said slip ring in a common plane, said slip ring and contact member being mounted for relative rotational movement and said brush arms having different lengths and different cross-sectional shapes.

6. An electrical contact device comprising, a slip ring, a contact member including a base member and a pair of resilient brush arms, said slip ring and contact member being mounted for relative rotational movement, said brush arms having different lengths and different cross-sectional shapes and said brush arms being arranged for planar' engagement with said slip ring in a common plane at different distances from the axis of rotation of said slip ring relative to said contact member.

7. In an electrical device, a rotatable operating shaft, -a slip ring having a flat, circular contacting surface, means to secure the slip ring 8 to the rotatable shaft, and a stationary contact member having resilient contact arms projecting into engagement with the slip ring, said Contact arms being of respectively different effective lengths, and at least one of said contact arms engaging said fiat circular surface of said slip ring at all times, said contact arms arranged to eng-age said slip ring at different distances from the center thereof and upon said fiat circular surface thereof.

WILLARD J. OPOCENSKY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 966,520 Bumiller Aug. 9, 1910 2,288,259 Gladulich June 30, 1942 2,343,306 Lear Mar. 7, 1944 2,350,968 Pratt June 6, 1944 2,434,740 Glaser Jan` 20, 1948 2,441,210 Schattle May 11, 1948 2,451,872 Rodgers Oct. 19, 1948 FOREIGN PATENTS Number Country Date 474,200 Great Britain Oct. 27, 1937 858,299 France May 6, 1940 

